Low-protein diet plus exercise a boon to CKD patients

A low-protein diet (LPD) combined with physical exercise provides significant benefits to patients with chronic kidney disease (CKD) by lowering blood pressure (BP) and improving glomerular filtration and cardiopulmonary function status, a study has shown.

"Although [more] studies are needed to establish the optimal approach to the application of this treatment in practice, our findings lend support to the use of LPD with additional physical exercise as a nursing strategy for nondialysis CKD patients,” the investigators said.

Randomized controlled trials published between 1 January 1956 and 17 May 2023 were searched using the databases of PubMed Central, Embase, Cochrane, and Web of Knowledge. The investigators searched for and appraised evidence on the effect of additional physical exercise on patients’ nutritional status and indicators of disease progression relative to LPD alone.

Close to 8,700 studies were identified, of which only nine (n=250 participants) met the eligibility criteria. LPD plus physical exercise resulted in a decrease in serum creatinine by a mean of –0.21 mg/dL (95 percent confidence interval [CI], –0.39 to –0.03) in CKD patients compared with LPD alone. [Eur J Clin Nutr 2024;78:737-747]

The addition of physical exercise to LPD also reduced BP, with systolic BP decreasing by –7.05 mm Hg (95 percent CI, –13.33 to –0.96) and diastolic BP by –5.31 mm Hg (95 percent CI, 7.99 to –2.62).

In subgroup analyses, resistance exercise proved to be beneficial to CKD patients, as shown by the reduction in estimated glomerular filtration rate (eGFR; –1.71 mL/min per 1.73 m², 95 percent CI, –3.29 to –0.14). The VO2 peak also increased by 2.41 mL/kg/min (95 percent CI, 0.13–4.70) when physical exercise was continued to 24 weeks.

Protein intolerance

“Most CKD symptoms are caused by protein intolerance,” the investigators said. “[S]ymptoms arise because the patient is unable to excrete [the] metabolic products of dietary protein and the ions contained in protein-rich foods.”

As a result, CKD patients accumulate salt, phosphates, uric acid, and nitrogen-containing metabolic products. They also encounter secondary problems of metabolic acidosis, bone disease, and insulin resistance. [Nephrology (Carlton) 2006;11:53-57]

"Therefore, protein intake in patients with CKD needs to be controlled to delay the onset of the need for renal replacement therapy as long as possible,” the investigators said.

Longer duration

An association was also observed between the more beneficial effects and the type and duration of exercise, with impedance exercise showing a side effect on parameters such as BMI and aerobic exercise exhibiting a less pronounced impact.

“In addition, short periods of exercise did not result in weight loss, and after prolonged cycles this increase disappeared and the increase in cardiorespiratory fitness was more pronounced,” the investigators said. “Therefore, it is possible to increase the duration of physical exercise to achieve a more beneficial effect.”

Large-scale, multicentre studies with longer exercise interventions and more sensitive indicators are warranted to confirm the effects of LPD plus exercise on patients with CKD, according to investigators.